Preliminary studies using the PH-20 surface protein of guinea pig spermatozoa have shown that immunized male guinea pigs had no spermatozoa in the epididymis and were infertile. These animals had circulating autoantibodies to PH-20, normal spermatogenesis and moderate inflammation of the testis. These results suggest the possibility that infertility was obtained in PH-20 immunized animals through the induction of sperm autoimmunity. Antigen-antibody reactions may have eliminated mature spermatozoa form the excurrent tract, a well-known "leaky" area of the male reproductive system. We suggest the hypothesis that the infertility effects of immunization with PH-20 can be separated from the inflammatory effects on the testis. This aim can be accomplished by an immunization regimen favoring humoral over "cell-mediated" (delayed-type hypersensitivity, DTH) autoimmune responses, either through the use of adjuvants different from complete Freund's adjuvant or immunization with "B cell" epitopes of PH-20. Since mouse PH-20 has been purified and characterized, we will establish an experimental model in inbred strains of mice known to be good or poor responders to spermatozoal antigens. We will also establish a model in monkeys, utilizing macaque PH-20, since experiments in non-human primates are essential before human vaccination is advocated. Our study will focus on the following Specific Aims: 1. Vaccinate male mice with PH-20. We will determine whether the immunization of male mice with murine PH-20 will result in reduction of their fertility, without causing inflammatory reactions in their testes or any other tissues. 2. Vaccinate male monkeys with PH-20. Following an approach similar to that used in the mouse model, we will investigate whether the immunization of male macaques with PH-20 autoantigen will result in reduction of their fertility, without causing orchitis or autoimmune damage to other organs. 3. Vaccinate male mice with synthetic peptides of PH-20. In this study, we will determine which peptides of PH-20 may result in reduction of fertility in male mice, without causing orchitis. We will focus on the evaluation of "B-cell epitopes", i.e. those determinants of PH-20 that preferentially elicit a humoral immune response rather than effector T cell responses (DTH and/or cytotoxic T lymphocytes). 4. Vaccinate male monkeys with synthetic peptides of PH-20. These experiments will be similar to those described in the preceding Specific Aim. Again, the focus will be on "B-cell epitopes". 5. Perform studies of PH-20 epitopes at the cellular level. The PH-20 protein and its synthetic peptides provide unique opportunities to investigate both epitopes and cellular interactions involved in autoimmune responses. We will develop a panel of murine CD4+ T cell clones specific for PH-20 and its "relevant" peptides, will isolate Th1 and Th2 clones and then will investigate their responses to PH-20 (including stimulation of B cells to produce antibodies).